It is known that certain microorganisms which grow on hydrocarbons produce and emit into the culture medium compounds having emulsifying properties, known as bio-emulsifiers. Such emulsifiers can be highly effective for producing oil-in-water emulsions with a variety of crude oils and petroleum fractions, so that the emulsifiers are useful for such applications as cleaning storage tanks, drums or barrels, tank cars, tankers, barges, pipelines and the like; for cleaning oil spills; and for enhanced recovery of oil from oil wells. Bio-emulsifiers produced in this manner are biodegradable, so that their use presents no pollution problems.
It is estimated that as much as two-thirds of the crude oil in an oil field cannot be recovered by conventional means because of the high viscosity of the oil. Crude oil is a complex mixture of paraffinic and aromatic hydrocarbons together with small quantities of oxygen, nitrogen and sulphur-containing compounds. As the proportion of higher hydrocarbons in the oil increases, its viscosity increases, thus increasingly impeding the flow of the oil through the pores of the oil-bearing rock formations.
Recent trends in methods for microbial enhanced oil recovery (MEOR) comprise the injection of certain microorganisms into the oil well. Although the practice has been to employ anaerobic bacteria for such purposes, it is assumed that use of hydrocarbon degrading aerobic bacteria would be much more effective, provided air under pressure can be injected together with the bacteria. The beneficial effects of such aerobic cultures arise from two sources: (1) the ability of the microorganism to degrade higher hydrocarbons, thereby reducing the viscosity of the oil; and (2) production by the microorganism of an emulsifier which leads to the production of an oil-in-water emulsion having a lower viscosity than that of the unemulsified oil.
The production of emulsifer during the growth on hydrocarbon substrates of certain strains of bacteria is known, e.g., Arthrobacter RAG-1 (Rosenberg et al., Applied Environmental Microbiology, March, 1979, pp. 402-408). Corynebacterium lepus (Cooper et al., Applied Environmental Microbiology, January, 1979, pp. 4-10); and Pseudomonas aeruginosa S.sub.7 B.sub.1 (Hisatsuka et al., Agr. Biol. Chem., Vol. 35, No. 5, pp. 686-692, 1971). The use of such organisms for reducing the viscosity of crude oil for enhanced secondary recovery has also been reported (Singer, et al., International Conferences on Microbiological Enhancement of Oil Recovery. Proc. of 1982, May 16, 1982, pp. 94-101).
Gutnick et al. U.S. Pat. Nos. 4,311,829, 4,311,830, 4,311,831 and 4,311,832 disclose emulsifiers produced by Acinetobacter Sp., A.T.C.C. No. 31012 (RAG-1) and the use of such emulsifiers in secondary recovery methods, for cleaning oil contaminated vessels, and in oil spill management.